Many devices, such as networking and computing devices (e.g., servers, switches, disk arrays, etc.), require the ability to update or replace faulty equipment without interrupting the functioning of the rest of the system. For example, a device may have a backplane to which a number of removable computing modules can be coupled. During operation of the device, modules may be added, removed, or replaced, as needed (e.g., to increase functionality of the device, to replace a failing module, etc.). However, inrush currents may be relatively high when making such changes. To protect against such currents, a hot swap circuit may be used to regulate the inrush current to a module while making changes to the modules of the device.
A power system typically has three stages. The first stage is a hot swap circuit which typically uses a very large size metal-oxide-semiconductor field-effect transistor (MOSFET) (such as a TO-247 package MOSFET, for example, but not limited to, FDH210N08) to prevent a damaging inrush current. The second stage includes a power brick including a full bridge inverter, a transformer and a rectifier. The transformer isolates the input and output side of the power brick and also steps down the input voltage. The third stage is a point of load (POL) which steps down the output of the power brick to the correct level for supplying to different chips. The hot swap MOSFET has some disadvantages including the space it occupies, the cost, a hot swap controller to control the MOSFET and since the hot swap MOSFET is in series in the main circuit, the conduction loss on the hot swap MOSFET make the system efficiency lower.